Subject: Re: [PATCH v2 1/2] net: dsa: ksz9477: add I2C managed mode support

From: Andrew Lunn <[email-masked]>
Date: Mon, 17 Dec 2018 08:38:46 +0100

On Sun, Dec 16, 2018 at 10:49:52AM +0100, Sergio Paracuellos wrote:
> In this mode the switch device and the internal phys will be managed via
> I2C interface.
> 
> Signed-off-by: Sergio Paracuellos <[email-masked]>
> ---
> Changes v2:
>     - Use dev->txbuf as transmition buffer which is allocated using
>       kernel allocators avoiding some possible DMA issues using the
>       stack.
>  drivers/net/dsa/microchip/Kconfig       |   6 +
>  drivers/net/dsa/microchip/Makefile      |   1 +
>  drivers/net/dsa/microchip/ksz9477_i2c.c | 269 ++++++++++++++++++++++++
>  3 files changed, 276 insertions(+)
>  create mode 100644 drivers/net/dsa/microchip/ksz9477_i2c.c
> 
> diff --git a/drivers/net/dsa/microchip/Kconfig b/drivers/net/dsa/microchip/Kconfig
> index a8caf9249d50..162fec43d204 100644
> --- a/drivers/net/dsa/microchip/Kconfig
> +++ b/drivers/net/dsa/microchip/Kconfig
> @@ -14,3 +14,9 @@ config NET_DSA_MICROCHIP_KSZ9477_SPI
>  	depends on NET_DSA_MICROCHIP_KSZ9477 && SPI
>  	help
>  	  Select to enable support for registering switches configured through SPI.
> +
> +config NET_DSA_MICROCHIP_KSZ9477_I2C
> +	tristate "KSZ series I2C connected switch driver"
> +	depends on NET_DSA_MICROCHIP_KSZ9477 && I2C
> +	help
> +	  Select to enable support for registering switches configured through I2C.
> diff --git a/drivers/net/dsa/microchip/Makefile b/drivers/net/dsa/microchip/Makefile
> index 3142c18b8f57..eb9b768face2 100644
> --- a/drivers/net/dsa/microchip/Makefile
> +++ b/drivers/net/dsa/microchip/Makefile
> @@ -1,3 +1,4 @@
>  obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ_COMMON)	+= ksz_common.o
>  obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ9477)		+= ksz9477.o
>  obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ9477_SPI)	+= ksz9477_spi.o
> +obj-$(CONFIG_NET_DSA_MICROCHIP_KSZ9477_I2C)	+= ksz9477_i2c.o
> diff --git a/drivers/net/dsa/microchip/ksz9477_i2c.c b/drivers/net/dsa/microchip/ksz9477_i2c.c
> new file mode 100644
> index 000000000000..3c9cba6e254b
> --- /dev/null
> +++ b/drivers/net/dsa/microchip/ksz9477_i2c.c
> @@ -0,0 +1,269 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Microchip KSZ series register access through I2C
> + *
> + * Author: Sergio Paracuellos <[email-masked]>
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +#include "ksz_priv.h"
> +
> +/* Enough to read all switch port registers. */
> +#define I2C_TX_BUF_LEN                  0x100
> +
> +/**
> + * ksz_i2c_read_reg - issue read register command
> + * @client: i2c client structure
> + * @reg: The register address.
> + * @val: The buffer to return the result into.
> + * @len: The length of data expected.
> + *
> + * This is the low level read call that issues the necessary i2c message(s)
> + * to read data from the register specified in @reg.
> + */
> +static int ksz_i2c_read_reg(struct i2c_client *client, u32 reg, u8 *val,
> +			    unsigned int len)
> +{
> +	struct i2c_adapter *adapter = client->adapter;
> +	struct i2c_msg msg[2];
> +	int ret;
> +
> +	msg[0].addr = client->addr;
> +	msg[0].flags = 0;
> +	msg[0].len = 2;
> +	msg[0].buf = val;
> +
> +	msg[1].addr = client->addr;
> +	msg[1].flags = I2C_M_RD;
> +	msg[1].len = len;
> +	msg[1].buf = val;
> +
> +	ret = i2c_transfer(adapter, msg, 2);
> +	return (ret != 2) ? -EREMOTEIO : 0;
> +}
> +
> +static int ksz_i2c_read(struct ksz_device *dev, u32 reg, u8 *data,
> +			unsigned int len)
> +{
> +	struct i2c_client *client = dev->priv;
> +	int ret;
> +
> +	len = (len > I2C_TX_BUF_LEN) ? I2C_TX_BUF_LEN : len;
> +	dev->txbuf[0] = (u8)(reg >> 8);
> +	dev->txbuf[1] = (u8)reg;
> +
> +	ret = ksz_i2c_read_reg(client, reg, dev->txbuf, len);
> +	if (!ret)
> +		memcpy(data, dev->txbuf, len);
> +
> +	return ret;
> +}
> +
> +static int ksz_i2c_read8(struct ksz_device *dev, u32 reg, u8 *val)
> +{
> +	return ksz_i2c_read(dev, reg, val, 1);
> +}
> +
> +static int ksz_i2c_read16(struct ksz_device *dev, u32 reg, u16 *val)
> +{
> +	int ret = ksz_i2c_read(dev, reg, (u8 *)val, 2);
> +
> +	if (!ret)
> +		*val = be16_to_cpu(*val);
> +
> +	return ret;
> +}
> +
> +static int ksz_i2c_read24(struct ksz_device *dev, u32 reg, u32 *val)
> +{
> +	int ret;
> +
> +	*val = 0;
> +	ret = ksz_i2c_read(dev, reg, (u8 *)val, 3);
> +
> +	if (!ret) {
> +		*val = be32_to_cpu(*val);
> +		/* convert to 24 bit */
> +		*val >>= 8;
> +	}
> +
> +	return ret;
> +}
> +
> +static int ksz_i2c_read32(struct ksz_device *dev, u32 reg, u32 *val)
> +{
> +	int ret = ksz_i2c_read(dev, reg, (u8 *)val, 4);
> +
> +	if (!ret)
> +		*val = be32_to_cpu(*val);
> +
> +	return ret;
> +}
> +
> +/**
> + * ksz_i2c_write_reg - issue write register command
> + * @client: i2c client structure
> + * @reg: The register address.
> + * @val: value to write
> + * @len: The length of data
> + *
> + * This is the low level write call that issues the necessary i2c message(s)
> + * to write data to the register specified in @reg.
> + */
> +static int ksz_i2c_write_reg(struct i2c_client *client, u32 reg, u8 *val,
> +			     unsigned int len)
> +{
> +	struct i2c_adapter *adapter = client->adapter;
> +	struct i2c_msg msg;
> +	int ret;
> +
> +	msg.addr = client->addr;
> +	msg.flags = 0;
> +	msg.len = 2 + len;
> +	msg.buf = val;
> +
> +	ret = i2c_transfer(adapter, &msg, 1);
> +	return (ret != 1) ? -EREMOTEIO : 0;
> +}
> +
> +static int ksz_i2c_write(struct ksz_device *dev, u32 reg, u8 *val,
> +			 unsigned int len)
> +{
> +	struct i2c_client *client = dev->priv;
> +	unsigned int cnt = len;
> +	int i;
> +
> +	len = (len > I2C_TX_BUF_LEN) ? I2C_TX_BUF_LEN : len;
> +	dev->txbuf[0] = (u8)(reg >> 8);
> +	dev->txbuf[1] = (u8)reg;
> +	i = 2;
> +
> +	do {
> +		dev->txbuf[i++] = (u8)(*val >> (8 * (cnt - 1)));
> +		cnt--;
> +	} while (cnt);
> +
> +	return ksz_i2c_write_reg(client, reg, dev->txbuf, len);
> +}
> +
> +static int ksz_i2c_write8(struct ksz_device *dev, u32 reg, u8 value)
> +{
> +	return ksz_i2c_write(dev, reg, &value, 1);
> +}
> +
> +static int ksz_i2c_write16(struct ksz_device *dev, u32 reg, u16 value)
> +{
> +	value = cpu_to_be16(value);
> +	return ksz_i2c_write(dev, reg, (u8 *)&value, 2);
> +}
> +
> +static int ksz_i2c_write24(struct ksz_device *dev, u32 reg, u32 value)
> +{
> +	/* make it to big endian 24bit from MSB */
> +	value <<= 8;
> +	value = cpu_to_be32(value);
> +
> +	return ksz_i2c_write(dev, reg, (u8 *)&value, 3);
> +}
> +
> +static int ksz_i2c_write32(struct ksz_device *dev, u32 reg, u32 value)
> +{
> +	value = cpu_to_be32(value);
> +	return ksz_i2c_write(dev, reg, (u8 *)&value, 4);
> +}
> +
> +static int ksz_i2c_get(struct ksz_device *dev, u32 reg, void *data, size_t len)
> +{
> +	return ksz_i2c_read(dev, reg, data, len);
> +}
> +
> +static int ksz_i2c_set(struct ksz_device *dev, u32 reg, void *data, size_t len)
> +{
> +	return ksz_i2c_write(dev, reg, data, len);
> +}
> +
> +static const struct ksz_io_ops ksz_i2c_ops = {
> +	.read8 = ksz_i2c_read8,
> +	.read16 = ksz_i2c_read16,
> +	.read24 = ksz_i2c_read24,
> +	.read32 = ksz_i2c_read32,
> +	.write8 = ksz_i2c_write8,
> +	.write16 = ksz_i2c_write16,
> +	.write24 = ksz_i2c_write24,
> +	.write32 = ksz_i2c_write32,
> +	.get = ksz_i2c_get,
> +	.set = ksz_i2c_set,
> +};
> +
> +static int ksz_i2c_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct ksz_device *dev;
> +	int ret;
> +
> +	dev = ksz_switch_alloc(&client->dev, &ksz_i2c_ops, client);
> +	if (!dev)
> +		return -ENOMEM;
> +
> +	if (client->dev.platform_data)
> +		dev->pdata = client->dev.platform_data;
> +
> +	dev->txbuf = devm_kzalloc(dev->dev, 2 + I2C_TX_BUF_LEN, GFP_KERNEL);
> +	if (!dev->txbuf)
> +		return -ENOMEM;
> +
> +	i2c_set_clientdata(client, dev);
> +
> +	ret = ksz9477_switch_register(dev);
> +	if (ret) {
> +		dev_err(&client->dev, "registering switch (ret: %d)\n", ret);
> +		return ret;
> +	}

Dan's comments appear to apply to this version as well.

      Andrew